Material condition estimation method, material condition estimation device, and program

Abstract

To enable easier estimation of material condition.SOLUTION: A material condition estimation method is provided, comprising acquiring vibration propagating through an inspection target while white noise vibration is being applied to the inspection target, and estimating the material condition of the inspection target on the basis of frequency characteristics at a characteristic frequency indicative of characteristics of a material of the inspection target included in frequency characteristics of the vibration propagating through the inspection target.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a material state estimation method, a material state estimation device, and a program. [Background technology]

[0002] The state of a material, such as the magnitude of the force when the material undergoes plastic deformation, must be measured by actually applying force to the material and bending it. In other words, by increasing the external force applied to the material and measuring the stress generated in the material when each force is applied, the magnitude of the external force at which the material undergoes plastic deformation can be identified. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-258879 A [Patent Document 2] JP 2003-270219 A [Patent Document 3] JP 2005-52212 A [Patent Document 4] JP 2011-5058 A Summary of the Invention [Problem to be solved by the invention]

[0004] To evaluate the material condition, mechanical properties are generally measured by tensile tests, etc. Also, it is necessary to prepare many materials to be measured. An object of the present invention is to provide a material state estimation method, a material state estimation device, and a program that can more easily estimate the state of a material. [Means for solving the problem]

[0005] One aspect of the present invention is a method for determining a material condition, which includes acquiring vibrations propagating through an object under test when white vibration is input to the object under test, and estimating a material condition of the object under test based on frequency characteristics at a characteristic frequency that indicates characteristics of the material of the object under test and is included in the frequency characteristics of the vibrations propagating through the object under test. Effect of the Invention

[0006] According to the present invention, the state of a material can be estimated more easily. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing an example of the configuration of a material state estimating system 1 according to a first embodiment. [Diagram 2] 4 is a flowchart showing the operation of the material state estimating device according to the first embodiment. [Diagram 3] 5A and 5B are diagrams illustrating an example of vibration input to an object to be inspected by a vibration input unit. [Figure 4] FIG. 13 is a diagram showing a change in the mechanical state, which is one of the material states, as an example of the received signal acquired by the received signal acquisition unit and the converted received spectrum. [Diagram 5] FIG. 1 is a diagram showing a change in a thermal state, which is one of the material states, as one example. [Figure 6] FIG. 13 is a diagram showing the results of estimating the mechanical state of an object to be inspected from the relationship with the received vibration spectrum acquired in advance while changing the mechanical state, as one example. [Figure 7] FIG. 11 is a diagram showing an example of the configuration of a material state estimating system according to a second embodiment. [Figure 8] 10 is a flowchart showing the operation of a material state estimating device according to the second embodiment. [Figure 9] FIG. 13 is a diagram showing the relationship between the tensile load applied to the test object and the received vibration spectrum. [Figure 10] 1 is a graph showing the relationship between tensile load and signal intensity at a characteristic frequency of a test object, and a graph showing the relationship between tensile load and stress of the test object. [Figure 11] FIG. 13 is a diagram showing the relationship between the tensile load applied to the test object and the received vibration spectrum when the type of material of the test object is changed. [Figure 12] 13 is a graph showing the relationship between tensile load and signal intensity at a characteristic frequency of the test object for each material of the test object, and a graph showing the relationship between tensile load and stress of the test object. [Figure 13] 13 is a graph showing the relationship between tensile load and signal intensity at a characteristic frequency of the test object for each material of the test object, and a graph showing the relationship between tensile load and stress of the test object. [Figure 14] FIG. 13 is a diagram showing a vibration input section and a vibration receiving section installed on a circular object under test. [Figure 15] FIG. 13 is a diagram showing how a vibration input section and a vibration receiving section are placed close to each other on a test object. [Figure 16] FIG. 13 is a diagram showing that a vibration input unit and a vibration receiving unit are installed on opposite sides of an object to be inspected. [Figure 17] FIG. 13 is a diagram showing how a vibration input unit and a vibration receiving unit are placed on an object to be inspected having a three-dimensional curved surface. [Figure 18] FIG. 13 is a diagram showing how a vibration input unit and a vibration receiving unit are placed apart on an object to be inspected having a three-dimensional curved surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a material state estimating system 1 according to the first embodiment. The material state estimation system 1 according to the first embodiment includes a vibration input unit 11, a vibration receiver 12, and a material state estimation device 13. The specimen 10s, which is the material to be measured, may be gripped by a mechanical method.

[0009] The vibration input unit 11 inputs vibration to the test object 10s. The vibration input unit 11 is, for example, a piezoelectric sensor such as an AE (Acoustic Emission) sensor or a piezo actuator. The frequency of the vibration input to the test object 10s by the vibration input unit 11 is controlled by an input vibration control unit 131, which will be described later. The vibration input unit 11 may input vibration in a non-contact manner, such as by using a laser or sound waves.

[0010] The vibration receiver 12 measures vibrations propagating through the test subject 10s. The vibration receiver 12 is, for example, an AE sensor or an acceleration sensor.

[0011] The material state estimation device 13 includes an input vibration control unit 131, a received vibration signal acquisition unit 132, a characteristic frequency identification unit 133, and a material state estimation unit .

[0012] The input vibration control unit 131 controls the frequency of the vibration input to the test object 10s by the vibration input unit 11. The input vibration control unit 131 may control the vibration input unit 11 to input white vibration including vibrations of multiple frequencies to the test object 10s, or may control the vibration input unit 11 to input vibration of a specific frequency.

[0013] The receiving signal acquisition unit 132 acquires the receiving signal measured by the vibration receiving unit 12. The receiving signal acquisition unit 132 converts the receiving signal into a receiving spectrum indicating the signal intensity for each spectrum. The receiving signal acquisition unit 132 calculates the receiving spectrum of the test object 10s, so that the receiving spectrum corresponding to the material state of the test object 10s can be calculated.

[0014] The characteristic frequency identifying unit 133 identifies a characteristic frequency of the test object 10s based on the relationship between the material state of the test object 10s to be estimated and the received vibration spectrum. The characteristic frequency is a frequency that represents the material state of the test object 10s.

[0015] The material state estimation unit 134 estimates a material state associated with the feature frequency identified by the feature frequency identification unit 133. The material state is, for example, a mechanical state, a mechanically deteriorated state, a chemically deteriorated state, a damaged state, a fatigue state, an adhesion state, a change in these material states, or a remaining life predicted from a change in the material state.

[0016] 2 is a flowchart showing the operation of the material state estimation device 13 according to the first embodiment. The input vibration control unit 131 controls the vibration input unit 11 to apply white vibration to the object 10s to be inspected (step S101). The vibration receiver 12 receives the vibration propagating through the object 10s to be inspected (step S102). The received vibration signal acquisition unit 132 frequency-converts the received vibration signal measured by the vibration receiver 12 to calculate a received vibration spectrum (step S103).

[0017] The characteristic frequency identification unit 133 identifies the characteristic frequency of the test object 10s from the reception spectrum based on the relationship between the material state to be estimated and the reception spectrum (step S104). The material state estimation unit 134 estimates the material state of the test object 10s based on the characteristic frequency (step S105).

[0018] The input vibration control section 131 controls the frequency of the vibration inputted by the vibration input section 11 to the test object 10s. The input vibration control section 131 may control the vibration input section 11 to input white vibration including vibrations of multiple frequencies to the test object 10s, or may control the vibration input section 11 to input vibrations of a specific frequency. Fig. 3 is a diagram showing an example of vibration inputted to the test object 10s by the vibration input section 11. The vibration shown in Fig. 3 is a vibration including vibrations of multiple frequencies, and has a substantially constant intensity with respect to the spectrum.

[0019] The receiving signal acquisition unit 132 acquires the receiving signal measured by the vibration receiving unit 12. The receiving signal acquisition unit 132 converts the receiving signal into a receiving spectrum indicating the signal strength for each spectrum. FIG. 4 is a diagram showing a change in a mechanical state, which is one of the material states, as an example of a receiving signal acquired by the receiving signal acquisition unit 132 and a receiving spectrum to be converted. The receiving signal acquisition unit 132 calculates the receiving spectrum of the elastic region before the mechanical state of the test object 10s changes, and the plastic region after the change, so that the receiving spectrum for the material state can be calculated.

[0020] The characteristic frequency identifying unit 133 identifies the characteristic frequency of the test object 10s based on the relationship between the material state of the test object 10s and the reception spectrum. The characteristic frequency is a frequency that represents the characteristics of the test object 10s. For example, the characteristic frequency is a frequency at which the signal intensity changes when the material state changes. FIG. 4 is a diagram showing the reception signal acquired by the reception signal acquiring unit 132 and the reception spectrum converted from the reception signal. In FIG. 4, the change in the reception spectrum when the material state of the test object 10s is changed is the largest in the frequencies around frequency f1, so the characteristic frequency identifying unit 133 identifies f1 as the characteristic frequency. The characteristic frequency identifying unit 133 may identify multiple frequencies, such as f1, f2, f3, and f4, as the characteristic frequencies.

[0021] The material state estimation unit 134 estimates the material state of the object under test 10s based on the relationship between the change in the material state of the object under test 10s and the signal intensity at the characteristic frequency of the object under test 10s.

[0022] In the above-described embodiment, the material state estimation unit 134 estimates the change in the mechanical state as the material state as the received vibration spectrum. However, the material state estimated by the material state estimation unit 134 is not limited to this. The material condition includes the mechanical condition, fatigue condition, damage condition, thermal condition, chemical reaction condition, chemical degradation condition, packing condition, swelling condition, density condition, and adhesion condition of the specimen.

[0023] 5 is a diagram showing a change in thermal state, which is one of the material states, as one embodiment of the present invention. It was observed that when the temperature of the test object 10s increases, the received signal and the received spectrum change.

[0024] The material condition estimation unit 134 may estimate the deterioration state, construction state, or change over time of the inspected object 10s by correlating the deterioration state, construction state, or change over time with changes in the received vibration signal intensity or received vibration spectrum. For example, the material state estimation unit 134 acquires in advance the relationship with the receiving spectrum and the characteristic frequency for each deterioration state of the test object 10s. After that, the material state estimation unit 134 uses the comparison result with the relationship with the receiving spectrum and the characteristic frequency acquired in advance to estimate the deterioration state of the test object 10s from the relationship with the receiving spectrum created by the receiving signal acquisition unit 132 and the characteristic frequency identified by the characteristic frequency identification unit 133. The material state estimation unit 134 may estimate the remaining life of the material from the estimated material state.

[0025] The material state estimation device 13 may be used to measure a reception spectrum accompanying a change in the material state of the test object 10s. In this case, the material state estimation device 13 includes a material state control unit 135. The material state control unit 135 controls the material state. The material state estimation device 13 records the relationship between the material state controlled by the material state control unit 135 and the reception spectrum of the reception signal received by the reception signal acquisition unit 132 when the test object 10s is in the corresponding material state. This allows the relationship between the material state of the test object 10s and the reception spectrum to be obtained.

[0026] 6 is a diagram showing the results of estimating the mechanical state of the test object 10s from the relationship with the received vibration spectrum acquired in advance by changing the mechanical state as one example. Linear regression analysis, which is one of the statistical processes, was used to estimate the material state, but other statistical processes or machine learning may also be used.

[0027] FIG. 7 is a diagram showing an example of the configuration of a material state estimating system 1 according to the second embodiment. The material state estimating system 1 according to the second embodiment includes, in addition to the components of the material state estimating system 1 according to the first embodiment, an inspected object material state change section 20. The material state estimating apparatus 13 according to the second embodiment includes, in addition to the components of the material state estimating apparatus 13 according to the first embodiment, a material state control section 135.

[0028] The inspection subject material state changing section 20 changes the material state of the inspection subject 10s. The inspection subject material state changing section 20 is, for example, a tensile machine that holds the inspection subject 10s and applies a tensile load.

[0029] The material state control unit 135 controls the inspected object material state changing unit 20 to control the material state of the inspected object 10s. For example, when the inspected object material state changing unit 20 is a tensile machine that grips the inspected object 10s and applies a tensile load, the material state control unit 135 controls the tensile machine to control the tensile load applied to the inspected object 10s.

[0030] After the material state control unit 135 changes the material state, the input vibration control unit 131 controls the vibration input unit 11 to input vibration to the test object 10s, and the received vibration signal acquisition unit 132 receives the vibration propagating through the test object 10s from the vibration receiving unit 12.

[0031] The characteristic frequency identifying unit 133 identifies a characteristic frequency of the object 10s to be inspected based on the relationship between the material state of the object 10s to be estimated and the received vibration spectrum. The material state estimation unit 134 estimates a material state different from the material state changed by the inspected object material state changing unit 20. The material state estimation unit 134 estimates a material state different from the changed material state based on the intensity change of a specific frequency in the received vibration spectrum when the material state is changed by the inspected object material state changing unit 20.

[0032] FIG. 8 is a flowchart showing the operation of the material state estimation device 13 according to the second embodiment. The material state control unit 135 controls the inspected object material state change unit 20 to change the material state of the inspected object 10s (step S201). The input vibration control unit 131 controls the vibration input unit 11 to apply white vibration to the inspected object 10s (step S202). The received signal acquisition unit 132 acquires the received signal received by the vibration receiver 12 (step S203). If the material state has not been changed and the received signal received a predetermined number of times (step S204: NO), the inspected object material state change unit 20 changes the material state to be applied to the inspected object 10s (step S205) and performs the operation from step S202. In addition, the received signal acquisition unit 132 converts the received signal into a received spectrum, and the material state estimation device 13 calculates the relationship between the material state of the inspected object 10s and the received spectrum.

[0033] The characteristic frequency identification unit 133 identifies the characteristic frequency of the test object 10s based on the relationship between the material state and the reception spectrum (step S206). The material state estimation unit 134 estimates a material state different from the changed material state of the test object 10s based on the characteristic frequency (step S207).

[0034] A case will be described below in which the inspected object material state changing section 20 controls the tensile load applied to the inspected object 10s, and the material state estimating device 13 estimates a material state different from the tensile load.

[0035] Fig. 9 is a diagram showing the relationship between the tensile load applied to the test object 10s and the received vibration spectrum. In the graph of Fig. 9, the vertical axis represents frequency and the horizontal axis represents tensile load.

[0036] The characteristic frequency identification unit 133 identifies the characteristic frequency of the test object 10s based on the relationship between the tensile load applied to the test object 10s and the vibration reception spectrum. For example, the characteristic frequency is the frequency at which the signal intensity changes most when the tensile load is changed. For example, in FIG. 9, the change in the tensile load when the tensile load applied to the test object 10s is changed is the largest at frequencies around f7, so the characteristic frequency identification unit 133 identifies f7 as the characteristic frequency.

[0037] The material state estimation unit 134 estimates the material state of the test object 10s based on the relationship between the tensile load applied to the test object 10s and the signal strength at the characteristic frequency of the test object 10s. FIG. 10 is a graph showing the relationship between the tensile load and the signal strength at the characteristic frequency of the test object 10s, and a graph showing the relationship between the tensile load and the stress of the test object 10s. When the tensile load is increased, the tensile load at which the signal strength at the characteristic frequency decreases is close to the tensile load at which the stress decreases, that is, when the test object 10s transitions from the elastic region to the plastic region. Therefore, the material state estimation unit 134 estimates the magnitude of the tensile load at which the signal strength decreases when the tensile load is increased at the characteristic frequency, for example, as the magnitude of the tensile load at the yield point at which the test object 10s transitions from the elastic region to the plastic region.

[0038] The material state estimation unit 134 may estimate the type of material of the test object 10s based on the characteristic frequency of the test object 10s. FIG. 11 is a diagram showing the relationship between the tensile load applied to the test object 10s and the reception spectrum when the type of material of the test object 10s is changed. As the type of material of the test object 10s, resin materials PMMA (Poly Methyl Methacrylate), PC (Poly Carbonate), POM (Poly Oxy Methylene), PP (Poly Propene), PTFE (Poly Tetra Fluoro Etylene), and PEEK (Poly Ether Ether Ketone) were used. In the diagram for each material in FIG. 11, the reception spectrum at the characteristic frequency is surrounded by a square. As shown in FIG. 11, the magnitude and number of the characteristic frequency differ depending on the type of material of the test object 10s. Therefore, the material state estimation unit 134 can estimate the type of material of the test object 10s based on the magnitude and number of the characteristic frequency of the test object 10s.

[0039] 12 and 13 are graphs showing the relationship between the tensile load and the signal intensity at the characteristic frequency of the test object 10s for each material of the test object 10s, and graphs showing the relationship between the tensile load and the stress of the test object 10s. In PMMA and PC, a phenomenon was observed in which the signal intensity increased as the tensile load approached the yield point at the characteristic frequency, and fracture and a decrease in signal intensity occurred immediately after the yield point. In POM, PP, and PTFE, a phenomenon was observed in which the signal intensity decreased as the tensile load approached the yield point at the characteristic frequency. In PEEK, a phenomenon was observed in which the signal intensity decreased as the tensile load approached the yield point at the characteristic frequency, and the signal intensity decreased rapidly after the yield point. Therefore, the material state estimation unit 134 can estimate a material state different from the tensile load by observing the change in signal intensity at the characteristic frequency of the resin material.

[0040] The characteristic frequency identifying unit 133 may identify a characteristic frequency of the test object 10s based on a change in signal intensity before and after the yield point of the test object 10s. In other words, the characteristic frequency identifying unit 133 may identify, as a characteristic frequency, a frequency at which the signal intensity increases or decreases as the tensile load approaches the yield point measured in advance.

[0041] The characteristic frequency identifying unit 133 may identify a characteristic frequency of the test object 10s based on a change in signal intensity before and after the yield point of the test object 10s. In other words, the characteristic frequency identifying unit 133 may identify, as a characteristic frequency, a frequency at which the signal intensity increases or decreases as the tensile load approaches the yield point measured in advance.

[0042] Other Embodiments 14 to 18 are diagrams showing, as one embodiment, cases in which the shape, size, installation interval, and installation location of the vibration input unit 11 and the vibration receiving unit 12 of the test subject 10s are changed.

[0043] FIG. 14 is a diagram showing a vibration input section 11 and a vibration receiving section 12 placed on a circular test object 10s.

[0044] FIG. 15 is a diagram showing that the vibration input section 11 and the vibration receiving section 12 are placed close to each other on the test object 10s.

[0045] FIG. 16 is a diagram showing that the vibration input section 11 and the vibration receiving section 12 are installed on opposite sides of the test object 10s.

[0046] FIG. 17 is a diagram showing a vibration input section 11 and a vibration receiving section 12 that are installed on an object 10s to be inspected that has a three-dimensional curved surface.

[0047] FIG. 18 is a diagram showing that a vibration input section 11 and a vibration receiving section 12 are placed apart from each other on an object 10s to be inspected having a three-dimensional curved surface.

[0048] The specific configuration of the material state estimation system 1 is not limited to that described above, and various design modifications and the like are possible without departing from the spirit and scope of the present invention. For example, when the type of material of the test object 10s is known and the characteristic frequency is also known, the input vibration control unit 131 may control the vibration input unit 11 to apply vibration of the characteristic frequency instead of white vibration to the test object 10s, and the material state estimation unit 134 may estimate the material state.

[0049] In the above-mentioned experimental results, a resin material is used as the test object 10s, but this is not limited thereto, and it is believed that the material state can be similarly estimated for, for example, metal materials, composite materials, and their joints and adhesives.

[0050] At least a part of the functions of the material state estimation device 13 may be realized by a computer. In that case, a program for realizing the functions of the material state estimation device 13 may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the functions. The computer system includes, for example, hardware such as a processor, an OS, and peripheral devices. The program of the material state estimation device 13 may be recorded in a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built into a computer system. The program of the material state estimation device 13 may be transmitted via an electric communication line. [Explanation of symbols]

[0051] 1 Material state estimation system, 11 Vibration input unit, 12 Vibration receiver unit, 13 Material state estimation device, 131 Input vibration control unit, 132 Received signal acquisition unit, 133 Feature frequency identification unit, 134 Material state estimation unit, 135 Material state control unit, 10s Test object, 20 Test object material state change unit

Claims

1. acquiring a vibration propagating through a test object when a white vibration is input to the test object; estimating a material state of the test object based on a frequency characteristic at a characteristic frequency that indicates a characteristic of the material of the test object and is included in the frequency characteristic of the vibration propagating through the test object; Material condition estimation methods.

2. identifying a characteristic frequency of the object to be inspected based on a relationship between a mechanical state, a fatigue state, a damage state, a thermal state, a chemical reaction state, a chemical deterioration state, a filling state, a swelling state, a density state, and an adhesion state of the object to be inspected and a receiving spectrum of a vibration propagating to the object to be inspected; The material condition estimation method according to claim 1 .

3. The test object is a resin material, a metal material, a composite material, or a bonding / adhesive member thereof. The material condition estimating method according to claim 2 .

4. a material state of the test object is changed, and a vibration propagating through the test object is acquired when a white vibration is input to the test object; estimating a material state of the test object that is different from the changed material state based on a change in intensity at a characteristic frequency that indicates a material characteristic of the test object and is included in a frequency characteristic of the vibration propagating through the test object; The material condition estimation method according to claim 1 .

5. A vibration input unit that inputs a white vibration to an object to be inspected, and a vibration receiving signal acquisition unit that acquires the vibration propagating through the object to be inspected; a material state estimation unit that estimates a material state of the test object based on a frequency characteristic at a characteristic frequency that indicates a characteristic of the material of the test object and is included in a frequency characteristic of vibration propagating through the test object; A material state estimation device comprising:

6. A program for causing a computer to execute the material state estimating method according to claim 1.

Images